This invention relates generally to a weighing system located on-board a vehicle, for weighing the load being carried by the vehicle.
For many commercial vehicles, e.g., common carriers, it is necessary to determine the weight being carried by the vehicle for sales transaction purposes or to ensure the vehicle is not overweight in violation of Weights & Measures Requirements. The accuracy of the scale is specified by government agencies and is certified as being "legal for trade".
As far back as 1960, companies have attempted to develop an on-board weighing scales for commercial vehicles that have a fifth wheel assembly, such as a tractor-trailer truck. The ability to measure the weight of the cargo contained in the trailer of a commercial vehicle in a simple manner with an on-board vehicle scale sufficiently accurate to be certified as "legal for trade" is very desirable. A "legal for trade" weighing scale avoids the necessity of having a truck go over a stationary legal scale to determine cargo weights.
Without an on-board vehicle scale, the truck must return to a facility where the changes in cargo weight can be determined. This is usually a facility that can weigh the whole truck prior to loading the cargo and after loading the cargo or vice versa. However, if cargo is partially off loaded, multiple trips to the weighing facility are necessary to determine the amount of cargo off loaded, which is time-consuming and inefficient. The truck may also have to stop at a highway weighing station to be weighed to see if it is overweight. If so, fines will be assessed. Therefore, most commercial trucking companies would like to be able to measure the weight of cargo being carried by a vehicle using an on-board vehicle scale. However, even with all of this need for a "legal for trade" on-board vehicle scale, success has been limited.
The only industry that currently uses on-board vehicle scales is the logging industry. However, these scales used by the logging industry have been unable to achieve the required accuracy and are not "legal for trade". Since the accuracy requirements are not obtainable with current on-board vehicle scales, these current on-board scales may only be used to determine approximate weights for the purpose of preventing overload fines, but may not be used to determine the weight for commercial transactions. In addition, these scales typically required costly maintenance and service and have been generally unsuccessful.
There are a number of commercial enterprises governed by the Interstate Commerce Commission regulations that charge a customer a fee based on the weight of the cargo or the weight of the material that is being sold to a customer, such as moving vans. In addition, liquid commodities, such as milk, ink and chemicals are often sold by weight as well as many bulk commodities, and are other examples of industries that could benefit from a "legal for trade" on-board vehicle scale. In fact, any industry that uses weight as a measure of quantity of goods or materials delivered may benefit from having an on-board vehicle scale that is certified "legal for trade".
Conventional on-board vehicle scales have never been certified as "legal for trade" because the sensing systems within these conventional on-board vehicle scales are not sufficiently accurate to meet the rigid tolerance requirements of a "legal for trade" weighing scale. In addition, most conventional on-board vehicle scales require the retro-fitting of existing vehicles which is very expensive. Some conventional on-board vehicle scales also require the insertion of weight sensors within the vehicle's chassis or weight bearing elements which may adversely affect the structural integrity of the vehicle.
Thus, there is a need for an on-board vehicle scale for measuring the weight of a load carried by the vehicle which avoids these and other problems of known systems, and it is to this end that the present invention is directed.